Question

A number is picked randomly in the range [0,7]. What is the probability that the number picked is between 3 and 5? What is the probability that the number picked is less than 4 knowing that the number usually picked appears to be in in the range [3,5]?

Answer 1

(1) 0.125

(2) 0.125

Explanation:

The total number of possible outcomes is:

N = 8

(1)

Compute the probability that the number picked is between 3 and 5 as follows:

Number of Favorable outcomes = 1

The probability is:

P (Number picked is between 3 and 5) = 1/8 = 0.125

Thus, the probability that the number picked is between 3 and 5 is 0.125.

(2)

The number usually picked appears to be in in the range [3,5], i.e. the numbers could be, {3, 4 or 5}.

Number of Favorable outcomes = n (Number < 4 and within [3, 5]) = 1

P (less than 4 ∩ within [3, 5]) = 1/8 = 0.125

Thus, the probability that the number picked is less than 4 knowing that the number usually picked appears to be in in the range [3,5] is 0.125.